Career
He built up a collection of some 50,000 specimens of bryophytes (mosses, lichens and liverworts) at his home in Hurstpierpoint, Sussex. The collection was largely made up of specimens collected around the world by other collectors and is now at the New York Botanical Garden, having been purchased after his death. These collectors included Richard Spruce and also Alfred Russel Wallace, who subsequently became Mitten"s son-in-law.
